The present invention relates to a carton clamp for lift trucks, for use in hoisting and handling loads in warehouses and the like in the form of packages such as large household appliances packed in corrugated cardboard cartons.
Lift trucks used for handling goods in warehouses and similar places may be equipped with specialized attachments intended to grip various types of loads securely. A lift truck may have a carton clamp including a pair of upright generally planar clamp arm assemblies extending forward from the lift truck and supporting generally parallel opposed clamp pads. The clamp arms are movable toward or away from each other laterally of the lift truck in order to grip or release a load such as a large carton enclosing a household appliance. Clamp pads carried on clamp arms of such a carton clamp are generally approximately flat and upright, and may have a height of about four feet (1.2 m) and a front-to-rear length of about four or five feet (1.2-1.5 m). Clamp pads may be unitary or provided as two separate clamp pad sections mounted on each clamp arm, one ahead of the other. A clamp pad may have a gripping surface of a resilient, non-slip material intended to be pressed against and grip a container or carton.
While most cartons or similar containers have parallel upright sides, because of the nature of the goods inside the carton and other packing material within the outer skin of a carton, it may be desirable to provide pressure against the exterior of a carton of a certain type in an uneven distribution, such as by providing greater pressure near the bottom of a carton and lesser pressure near the top of the part of the carton engaged by the clamp arm assembly.
It is desirable for the clamp pad or clamp pads to be free to at least a small extent, to articulate about a vertical axis in order to accommodate clamp arm deflection and conform better to the shape of a carton and, to some extent, the contents of the carton. This capability is addressed in prior art Link, U.S. Pat. No. 3,643,827, for example, which discloses clamp pads mounted on carton clamp arms in a way which allows a small amount of articulation about a vertical axis.
European patent EP 1 997 771 B1 discloses a lift truck clamping attachment for handling cartons in which clamping pads are preloaded to be elastically deformed and present a concave surface toward the surface of a carton to be grasped. The pressure provided by the clamp jaws is intended to provide uniform distribution of the clamping pressure on the packages to be hoisted and transported so that there are no important specific pressure gradients with respect to the average value of pressure against a package being grasped.
In some cases, however, rather than having a uniform pressure exerted over the entire surface contacted by a clamp pad, it is desired to have a definite pressure gradient, or to provide greater pressure in a particular part of the clamp pad. In accordance with the present disclosure two or more, and preferably three, coaxial pivoting clamp pad mounts, or support assemblies, are carried on a carton clamp arm and provide adjustable spacing between the axis of rotation defined by the coaxial pivoting support assembly and a clamp pad supported by the mounts, so that a radial distance away from the axis of rotation of the pivoting support assembly can be adjusted to mount a clamp pad at a desired attitude, varying from the orientation of the pivot axis by a small angle in order to provide a definite pressure gradient between an uppermost part and a lowermost part of a clamp pad as it is urged into contact against an outer surface of a carton to be grasped by the carton clamp assembly. Alternatively, the pivoting clamp pad support assemblies can be adjusted to provide radial spacing between the pivot axis and a particular part of a clamp pad that will result in a greater pressure at either or both of the top and bottom, or at a mid-height location, or at the front or the rear, of a clamp pad.
The foregoing and other features of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.